8th INTERNATIONAL WHEAT CONFERENCE

dRoughT STReSS ToLeRANCe IN CeReALS IN TeRmS of
WATeR ReTeNTIoN CAPACITy ANd ANTIoxIdANT eNzyme
ACTIVITIeS
S. Bencze, Z. Bamberger, K. Balla, T. Janda, Z. Bedő
and O. Veisz
Agricultural Research Institute of the Hungarian Academy of Sciences, Martonvasar,
Brunszvik u. 2. H-2462 Hungary
E-mail Address of presenting author: benczesz@mail.mgki.hu
The drought stress tolerance of cereals was investigated in PGV-36 growth chambers in
the phytotron. Winter wheat (Mv Mambo, Mv Regiment), spring wheat (Lona), winter
durum (Mv Makaroni) and winter barley (Petra) varieties were selected for the tests.
Seedlings in the one-leaf stage were planted four to each 3-litre pot directly or after vernalization.
Water was withheld for seven days starting from the 10 th day after the heading
of each genotype. During water stress the control soil moisture content of 22-30% (volumetric
water content) decreased to around 6 VWC%. Leaf samples were collected and
analyzed for water content and the activity of glutathione reductase (GR), glutathione-Stransferase
(GST), guaiacol peroxidase (GPX), catalase (CAT) and ascorbate peroxidase
(APX) at various soil water levels. The aim of the experiment was to characterize the relationship
between drought stress tolerance and changes in the antioxidant enzyme system,
and to determine whether it has a predictive value. Under the very intense drought shock
conditions created, clearly visible differences in tolerance were detected between the varieties.
Genotypes with lower water retention capacity started to wither after 3-4 days. Petra
exhibited a severe drop in leaf moisture content under water stress. Mv Pehely and Mv
Makaroni also lost more than 6% leaf water at the 8-12 % soil moisture level, while Lona
only lost turgor pressure under more severe water stress. Winter wheat varieties tolerated
water withdrawal the best. Mv Regiment lost very little water, though the decline was in
linear relation to the soil water content, and the plants did not start to wilt until the 5-6 th
day. Mv Mambo proved to have excellent drought resistance as it was able to maintain
normal functioning for a long time without losing any moisture. Water loss was minimal
even when water stress was most intense. The antioxidant enzyme system was clearly
related to the water withholding capacity of the varieties. Genotypes with lower tolerance
had increasing activity levels for all antioxidant enzymes, parallel to the severity of water
stress, indicating strong general oxidative stress. These varieties, however, exhibited the
lowest antioxidant enzyme activity levels, which, even under stress conditions, did not
reach the lowest values recorded for genotypes with better tolerance. Lona, which was
slightly more tolerant to drought, had much higher peroxidase activity (GPX) than the
average even under control conditions, though it had low values for the other four enzymes.
In this variety, however, the GPX activity did not change due to water stress, while
APX became markedly more active even under mild stress. The activities of GST, CAT
and GR also increased slightly as the water stress became more severe.
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